Frequency converter



June 19, 1928.

W. T. POWELL FREQUENCY CONVERTER Filed March 1923 FlG.1

HO V.

IOO V.

FIG. 2

OSCILLATOR HOV.

INVENTOR W) N FRED T. POWELL 8% W ATTORNEY Patented June 19, 19 2 8.

' UNITED STATES I 1.674.297 PATENT. OFFICE.

WINIRRD '.l'.. POWELL, O! ROCHESTER, NEW YORK, ASSIGNOR TO THE STROI'BERG-' OARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK,

CORPORATION 01 NEW YORK. V

rmieumrcr convnaran.

Application filed larch 8, 1928. Serial No. 828,281.

This invention relates to a ringing current machine and more particularly to that type of a ringing current machine known as a frequency converter.

- In former ringing current devices .ithas been customary to employ mechanical rectifiers and also a mechanical vibrator cooperating therewith to transform the current derived from the commercial power circuit into ringing current of proper frequency and voltage to operate the signal or bell at a telephone station. Such an arrangement has the disadvantage that the contacts of the vibrators and the mechanical rectifiers must be provided with heavy contact points and be protected by spark condensers. Such an arrangement has also the disadvanta e that noises are introduced into the stora e attery of the telephone exchange due to t e opera- 2 tion of the various vibrators therefrom.

The present invention has for its purpose the use of one or more thermionic device's instead of one or more of the mechanical devices as now used in such frequency converters. I

Other featuresof the invention will appear from the description and appended claims.

In the drawings Fig. 1 diagrammaticall represents the circuit arrangement by whic a commercial source of current of- 110 volts and 60 cycles frequency is converted into ringing current of 100 volts and cycles frequency. Fig. 2 is a circuit arrangement similar to that disclosed in Fig. 1 except that all of the controllers including the oscillator are of the thermionic tube type.

It is believed that the invention will best be understood'by describing the circuit operation of the diagram of Fig. 1. At the left of this figure there is represented a source of current of 110 volts and 60 cycle frequency which is connected across the primary of the transformer 5 designed to step u the voltage to 350 volts. The secondary of this transformereis connected through the upper section 7 of a second transformer 6 to the plate 8 of a vacuum tube, generally designated 9. The other end of the secondary coil of the transformer 5 is connected over conductor thnough the lower section 10 of the transformer 6 to the plate 11 of a second vacuum tube generally designated 12. Conductors 13, 22 and 24 areconnected at such points of The pendulum controlsa pairof contacts 18 to interrupt the operating circuit of the ele'ctromagnet 16 whichincludes the local battery 19. I

In the operation of the converter, at that portion of the wave of originating current transmitted to the transformer 5 when the secondary terminal 20 is positive, the plate 8 of the vacuum tube 9 is positive permitting current to flow in the plate-filament circuit of the vacuum tube 9. This plate filament circuit may be described as extending from the plate 8 to the primary winding of the transformer 6, conductor 23, secondar winding of transformer 5, conductor 24, t e filament 15 of the vacuum'tube 9.. When the terminal 21 of'the secondary winding 'of the transformer 5 is positive, theplate 11 of the vacuum tube 12 is made positive over conductor 25 so that current flows in the platefilament circuit of this last named vacuum tube. It will be noted that the plate circuits of both of these mentioned vacuum tubes include the primary windings 7 and 10 of the transformer 6. The transformer is of such design that if the vibrator were omitted, current of 100 volts and 60 cycles would be induced in the secondary of this transformer. The function of the mechanical vibrator is to change the current in the out-put circuit to a frequency of 20'cycles.

The vibrator is designed to oscillate or vibrate at a frequency of 20 cycles and its contacts 26 and 27 are closed at each half cycle that is forty closures per second. On each closure of each of the contacts 26 and 27, a source of negative potential from battery 19 is connected to the grids 28 and 29 of the vacuum tubes 9 and 12 thus blocking the current flow through these vacuum tubes forty times out of sixty with the result that 20 cycle current is produced in the out-put generally designated "replaces the me .'chanical vibrator of 'Fig. 1. I It is believed to bef'unnecessary to describe the operation 7 of the vacuum tubes 31 and 32 since their operation is identical with that of the vacuum tubes 9 and 12 of Fig. 1. The oscillator 40 is desi ed to apply negative potential to the gri s 33 and 34 forty times each second, in the same manner as the vibrator 20. a

While the specific valuesof voltage and frequency have been referred to, it will be understood that this referenceis-simply for urposes of description and that there may lie wide variations in voltage and frequency introduced in the in-putcircuit and that the constants of these circuit-s may be so varied that the out-put voltages and frequencies may be likewise greatly varied. The operation of the vacuum tube oscillator is also not limited to the specific number of oscil-' lat-ions referred to in this description.

What is claimed is:

1. In a frequency-converter for signaling systems and the like, a source of alternating current, a transformer having a. primary winding and a secondary winding, a circuit serially including said primary winding and said source of alternating, current, a plurality of thermionic devices, each having a filament, a plate and a id, each of said filaments beingconnectecl across a'portion of said secondary winding, grid circuits connecting said grids and said filaments, a second transformer having primary and-secondary windings, the plate elements of said thermlonic devices being connected to the secondary winding of said first transformer throu h a primary winding of said second transfbrmer, and an additional thermionic device having a plate circuit and a grid circuit arranged to interact, said last mentioned thermionic device being arranged to control said first mentioned grids.

2. Ina frequency converter for signaling systems and the like, a source of alternating current, a transformer having a primary winding and a secondary winding, a circuit including said primary winding and said source of alternating current, a plurality of thermionicdevices, each having a filament, a plate and a grid, means for rendering said filaments active including a portion of said secondary winding, said ids being connected in multiple to the mid-point of said secondary winding, a second tramformer having primary and secondary windings, the plate elements of said thermionic devices being connected to the secondar winding of said first transformer through a primary winding of said second transformer, an additional thermionic device provided with interacting grid and plate circuits, said last mentioned plate circuit being inductively associated with said first mentioned grids, and an outgoing circuit connected to the secondary winding of said second transformer.

3. In ,a frequency converter for signaling systems and the like, a source of alternating current, a transformer having a primary winding and a secondary winding, a circuit including said primary winding and said source of alternating current, a plurality of thermionic devices, each having a filament,

a plate and agrid, each of said filaments being connected across a'portion of said secondary winding, said grids being connected in multiple to the mid-point of said secondar winding and being connected to said filaments to form grid circuits having a portion in common, a winding of an induction coil in said common rtion of said grid circuits, a second trans ormer having primary and secondary windings, plate elements of said thermionic devices connected to the secondary winding of said first trans former through a primary winding of said second transformer, an additional thermionic device provided with interacting grid and plate circuits, a second winding of said induction coil in said last mentioned plate circuit inductively associated with the winding in/said grid circuits, and an outgoing circuit connected to the secondary winding of said second transformer.

In witness whereof, I hereunto subscribe my name this 2nd day of March, A. D. 1923.

WINFRED T. POWELL. 

